The elder son of Ptolemy
XII was not yet 12 when his father died (51 BCE), leaving him as
co-ruler of Egypt with his older sister, Cleopatra
VII. Seeing that he was more pliable than his strong-willed sister,
the de facto regent [Pothinus] had Ptolemy designated as senior
ruler. That only intensified the sibling rivalry & led to
Cleopatra's expulsion from Egypt in the spring of 48 BCE.

Cleopatra's expulsion, however, precipitated open
civil war that ended with direct Roman occupation of Egypt. With the
support of Arab allies, she laid siege to the Egyptian frontier city
of Pelusium. Meanwhile, Ptolemy's Roman patron Pompey,
whose
forces had been decisively defeated by those of Julius
Caesar at the battle of Pharsalus [Greece], sought refuge at Pelusium. To court the favor of the Roman victor
[Caesar],
however, the 15 year old king's advisors had him lure Pompey into an ambush as he came
ashore. This brought Caesar to
Alexandria. Both Ptolemy & Cleopatra were brought to Caesar's camp
& forced to accept formal reconciliation. This settlement did not
produce civil peace, however. Since Caesar had the legitimate
rulers of Egypt in his custody, Pothinus & others in the court of
Alexandria championed their sister ArsinoŽ
& laid siege to the city of Alexandria. ArsinoŽ, however, quarreled
with the leaders of the Egyptian forces. So they offered to exchange
her for Ptolemy who, no longer constrained to submit to a Roman dictated
dťtente, took command of the siege. As a strategist, however, the 15 year
old god-king was no match for the wily Caesar. With his troops
reinforced by allies from Pergamum [Asia Minor], Caesar broke the siege.
Ptolemy drowned while fleeing the battlefield, leaving Caesar in position to dictate the
future of Egypt.